Hereinafter, a handover and ranging procedure will be briefly described.
Handover indicates a function for maintaining a communication call when a mobile station (MS) moves in a zone such as a cell of a base station (BS) to the zone of another BS during the communication call (a function for switching a channel or a line and continuously maintaining a call).
The handover may be divided into softer handover, soft handover and hard handover.
At this time, the softer handover indicates handover which is performed in one cell and indicates that an MS switches a used channel to a good channel within a cell coverage. The soft handover indicates that two adjacent channels are simultaneously operated and then one of the channels is gradually disconnected. The soft handover can be readily implemented because the same frequency band is used in a code division multiple access (CDMA). The hard handover indicates that a channel which is currently used is disconnected and then another channel is immediately connected.
When the MS moves from the cell of a BS which currently provides a service, to the cell of another BS, the MS performs a ranging procedure after performing handover to another BS.
The ranging indicates a set of processes of maintaining connection quality (in particular, synchronization) of radio frequency (RF) communication between a BS and an MS. Ranging is not problematic at the time of multiple access based on an OFDMA/TDD scheme because the BS transmits a signal to several MSs in downlink. However, in uplink, since several MSs transmit respective signals, propagation delay is changed according to the MSs. Accordingly, the BS and the MSs perform ranging by separate timing synchronization methods. That is, the ranging procedure is a procedure of correcting synchronization of transmission times of the several MSs.
For uplink synchronization acquisition and power control between the BS and the MSs, the ranging includes initial ranging, periodic ranging and hand-off (HO) ranging. The ranging further includes bandwidth request (BR) ranging for, at the MS, requesting a bandwidth to the BS.
The initial ranging is used for initial network entrance and connection when the MS first enters the BS (e.g., the power of the MS is turned on or a sleep mode is switched to an idle mode). The periodic ranging is periodically transmitted from the MS to the BS for synchronization tracking. The HO ranging is performed by the MS for synchronization with a target BS during handoff. The BR ranging is transmitted to the BS for requesting uplink allocation. The BR ranging is transmitted from only MSs which was already synchronized with the system.
When the BS receives a ranging request message from an MS, the BS generates a connection identifier (CID) of the MS. Thereafter, the BS performs renegotiation, re-authentication and re-registration processes with the MS.
The CID indicates an address for distinguishing and identifying connections mapped to a necessary service flow between peer entities on a MAC sub-layer. The CID is located in an MAC PDU header. That is, all the connections between the BS and the MSs are identified by the CID included in the MAC header and the CID corresponds to a service flow identifier (SFID) for defining service flow quality of service (QoS) parameters associated therewith.
A management CID may be allocated from the BS to the MSs when all the MSs are initially connected to the BS. That is, the MSs may receive the management CID from the BS by a series of ranging and registering processes. The management CID may be divided into a basic CID, a primary CID and a secondary CID.
At this time, the basic CID (BCID) is used when the BS identifies the MS in an initial connection stage. That is, the MAC address of the MS is mapped to the BCID. The primary CID (PCID) may be used in an authentication message and messages associated with dynamic resource allocation. The secondary CID (SCID) is optional and, in an MS capability negotiating process, it may be determined whether or not the SCID is used.
In addition to the management CID, the CID includes a transport CID (TCID) for identifying a user traffic service, a broadcasting CID (BCID) for identifying broadcasting traffic and a multicasting CID (MCID). The TCID may be allocated in every connection generated between the MSs and the BS.
Generally, an MS performs handover from a serving BS to a target BS, and the target BS acquires synchronization via ranging and updates CIDs used in the target BS. As a communication technology has been developed, there is a need for a method of performing fast handover in order to reduce a delay time at the time of handover.
Accordingly, in order to perform faster handover and ranging, there is a need for a method of allocating a new CID in addition to a method of allocating a CID which is generally used.